There are numerous situations where wheels are placed in close proximity to one another in axially-parallel tandem configurations. For example, the wheels of a roller conveyor system are so configured, as are the wheels of tandem truck or truck trailer. In many situations it is desirable to provide a braking force to the wheels and there are numerous examples in the prior art of devices that can apply a braking force to wheels that are configured in tandem.
U.S. Pat. No. 2,590,994 to McKay discloses a braking apparatus for roller conveyors. The apparatus comprises an elongated block that is generally wedge-shaped and is located between two adjacent rollers. The narrower edge of the block is downwardly positioned. The apparatus has means to move the block in a generally vertical direction in order to cause the sides of the block to frictionally engage the rollers and thereby the block applies a braking force to the rollers.
U.S. Pat. No. 5,086,903 to Agnoff discloses a tandem wheel brake roller system for use in gravity conveyors. A brake roller is mounted below the conveyor. Two floating rollers are rotatably mounted above the brake roller. When a load bearing item engages the floating rollers, the floating rollers are forced downward into engagement with the brake roller. The brake roller thereby applies a braking force to the floating rollers.
U.S. Pat. No. 5,381,680 to Rauch discloses a retractable wheel lock assembly that includes a telescoping security tube on which a wedge-shaped brake member is mounted. The security tube is moveable between a first, retracted position and a second, extended position. The wedge-shaped brake member frictionally engages the wheels when the telescoping security tube is moved to the extended position. The brake-member thereby applies a braking force to the wheels.
Although the prior art has many examples of braking systems for tandem wheels, it is heretofore unknown to provide a braking system that can apply a braking force to one of the wheels in direct reaction to the other wheel being stopped through external forces. For example, in a roller conveyer system, the wheels may be mechanically driven by an external drive shaft and one of the wheels may experience a loss of mechanical drive. In that situation, it would be desirable to immediately stop the adjacent wheels from rotating. Currently, one might employ an electronic sensing system to determine that a particular wheel had stopped and the system could then command other elements to provide braking force to the adjacent wheels using one of the prior art devices. However, it would be desirable to have a purely mechanical system that could immediately apply a braking force to an adjacent rotating wheel in direct reaction to the stoppage of one of the other wheels, regardless of the reason for the stoppage.
It is therefore an object of the present invention to provide an improved braking system for axially-parallel tandem wheel configurations.
It is another object of the present invention to provide a braking system for axially-parallel tandem wheel configurations that utilizes the forces created by the mechanically driven wheels to provide the braking forces needed to brake one of the wheels when one of the other wheels is braked due to external forces.
The present invention addresses these objects as well as other problems associated with braking systems for axially-parallel tandem wheel arrangements. The present invention provides a block that is shaped to conform to a portion of the circumferential surface of each of the wheels. The block is positioned to be in continuous frictional engagement with the circumferential surface of each of the wheels so that a constant force is applied to each of the wheels. When one of the wheels is stopped due to an external force, the mechanical forces that are built through the continuous frictional engagement result in the block exerting a braking force against the circumferential surface of the other wheel.